Don't ever look at what the big boys do (IBM, Amazon, Microsoft, EBay,etc) The big boys do not need great websites. They can afford to force you to use their mess of the website. Do what great web designers do, with the absolute emphasis on "web".
Then make it look great - but that's just me
Do you need a professional? Again it really depends on what you need. Is it your business site? Then I would always ask for professional help if you feel unsure you doing the right thing. Is it little personal portfolio or blog? Go ahead and play away as long as you're having fun
Hope this helps, if you need any assistance, give me a shout.
A very important thing is the target group. Do not design anything how you prefer, what you find easy to use, or the colours you like. Investigate and make a good profile of the target group and design with that in mind.
the best and most simple rule is to think like a user ! and to know what is the audience of the web
the next important thing is to create the layout and it must be easy to navigate. everything must be visible
then you can add some accents and design the main idea using illustrator or photoshop in 72 dpi (1000x700)
Well since it seems like you want to go into web design, i've provided a helpful link below. And even if you don't really want to go into freelance, this link could still be helpful.
Check it out: The Roadmap To Becoming A Professional Freelance Web Desinger
NOTE: The web page is super long ^^
EDIT: Hmmm. There seems to be an error. Apparently, I can't post website links just yet since I'm a new member...Oh well, if you search that in google, the topic should pop up under "Smashing Magazine". You should totally read it.
Here is 10 Principles Of Effective Web Design if you remember it than you can make good web site.
1. Don’t make users think
2. Don’t squander users’ patience
3. Manage to focus users’ attention
4. Strive for feature exposure
5. Make use of effective writing
6. Strive for simplicity
7. Don’t be afraid of the white space
8. Communicate effectively with a “visible language”
9. Conventions are our friends
10. Test early, test often